Crenelated polishing pad



ci. 24, 19? W. E. BECKER 3,348,256

CRENELATED POLISHING PAD Filed May 25, 1965 To e w 7 :h JVS M um 5gg m,M M

/ w' ul nu 95 ull: Il f PRESS ATTORNEYS United States Patent 3,348,256CRENELATED POLISHING PAD William E. Becker, Raynham, Mass., assignor toBacon Felt Company, Taunton, Mass., a corporation of Massachusetts FiledMay 25, 1965, Ser. No. 458,655 9 Claims. (Cl. 15-230.12)

ABSTRACT OF THE DISCLOSURE This invention relates to an improvedmechanically held polishing member of the typeL used in polishinglateral surfaces of glass, marble, and other large plane hard surfacesand especially to such felt' thickness as to be relatively unbendable.

In the at glass industry mechanical-chemical operations, such aspolishing, cleaning and washing, are performed on the surfaces of glasswhile it is being conveyed through the operation in either sheet form,or as a continuous ribbon.

In either case, the polishing or cleaning operation is accomplished bycausing a plurality or rotating pad- .covered polishing units to pressagainst and slide over the glass surface. The pad face is saturated withthe appropriate cleaning or polishing compounds and depending upon theoperation it may be used either on the top, or the bottom, of the glasssurface and in some cases simultaneously on both surfaces.

As the pad surfaces wear away, they must be replaced .by attaching newpads to the polishing blocks. This attachment may consist of amechanical holding device, or it may be accomplished by adhesivelybonding the felt to the polishing block.

Traditionally, the polishing felts lhave been held mechanically bycausing the four corners of a square felt to bend around the outerperiphery of the circular metal vpolishing block for locking thereon `byan outer locking ring or band, which is hydraulically pressed on to andover the upturned corners of the polishing felt. This method of holdingfelt in place has been widely accepted as a positive and practicalprocedure. However, it has the disadvantage that it is limited to feltof about one inch thickness,.which necessitates frequent changes.`

Other disadvantages of this type of mechanically held relatively thin,square, polishing felt, embodied in theA pressed-on ring method, is thatperfect alignment to the block and uniform tautness across the block areimpossible to achieve. IUnless the felt is relatively true on the blockand has the proper tension, the possibility of cyclic fatigue or wedgedWear exists.

The relatively thick, circular, adhesively secured polishing felts ofthe type described in my United States Patent No. 3,038,279, issued June12, 1962, have not heretofore been adaptable to the conventional systemof holding felt with a pressed-on steel ring.

The method of holding the polishing felt in place by adhesive attachmenthas been less widely accepted in that special care must be exercised inobtaining clean surfaces to which to apply the adhesive. Curingprocedures must be closely supervised and properly conditioned cementsmust be employed. Special provisions must also be made to handle thecementing operation, whether it be of the hot melt or solvent releasetype, by way of adequately ventilated rooms adjacent to the polishingoperation. In addition, the increasing demand of lower operating costsand higher speeds has resulted in the thermal failure of many adhesivebonds. There are no thickness limitations with adhesively held polishingfelt.

I am aware that it has heretofore been proposed to provide a yieldablefelt pad Within an outer, relatively thin covering sheet, the sheethaving a series of tongues therearound for bending to the shape of apolishing block. Bufng heads of this type are shown in United StatesPatents 505,644 to Perry of Sept. 26, 1893, United States Patent 528,024to Perry of Oct. 23, 1894, United States Patent 631,675 to Rogers ofAug. 22, 1899, and United States Patent 736,736 to Kane of Aug. 18,1903. However, in pads of this type the tongues are bent from a thinbendable sheet material for distortion to conform to the shape of theblock and the felt, if any, is inside the sheet while in this inventionthe felt is relatively thick and on the outside of the reinforcing sheetwith the felt tabs preformed without bending to conform to the shape nof the block.

The principal object of this invention is to provide a relatively thickcrenelated, composite, polishing pad of felt, the crenelated feltportion upstanding integrally around the upper periphery of the pad withits alternate solid felt intervals resiliently wedged under the lockingring and with the block engaging faces of the pad covered by areinforcing backing. Y

A further object of this invention is to provide a composite polishingpad having preformed, upstanding, reinforced tabs of felt therearoundfor mechanical attachment to the polishing equipment with no modicationsto the existing holding devices.

Another object of this invention is to provide a composite polishingpad, which may be held by existing mechanical equipment and which may beused in substantially greater thickness than heretofore possible.

A further object of the invention is to provide a relatively thickcomposite polishing pad, which eliminates the need for adhesive bonding,assures a more positive hold and allows greater stresses to be appliedthrough the polishing pad.

Another object of the invention is to provide a polishing felt ofsubstantial thickness formed of vertically disposed felt strips retainedlaterally by an annular felt ring, the ring having preformed, integral,felt tabs normally extending up the side of a steel polishing block toprovide a resilient wedge between the block and a steel ring which hasbeen pushed on hydraulically.

Still another object of the invention is to provide a polishing pad madeup of vertically oriented felt segments held together by an outer feltring having preformed, up-

standing felt tabs therearound, by a rubber fabric backing extendingover the entire back of the composite and reinforcing the holding tabs,which extend up between the ,steel block and steel ring, and by at leastone compression band extending around the pad.

Still another object or" the invention is to provide a relatively thickpolishing pad, which may be applied without adhesive to the polishingblock with uniform alignment and tension and which will operate withuniform and even polishing motions.

Additional objects and advantages of the method of making the compositepolishing pad and the improved polishing member will be apparent fromthe claims, the

description of the drawing, and from the drawing in which:

FIGURE l is a side elevation, in half section, of the crenelated,composite, polishing felt of the invention,

FIGURE 2 is a perspective view on a smaller scale of the felt shown inFIGURE 1,

FIGURE 3 is a plan View, with a portion of the backing broken away, ofthe felt shown in FIGURE 2,

FIGURE 4 is a fragmentary side elevation, with part broken away, showingthe crenelated felt of the invention mounted on a polishing block,

FIGURE 5 is an exploded view, on a smaller scale, showing the doubled,crenelated, reinforcing backing and the crenelated felt ring anddisc-shaped felt body, and

FIGURE 6 is a diagrammatic, fragmentary, side elevation showing the stepof adhesively uniting the parts shown in FIGURE 5, into a unitized,crenelated felt polishing pad.

A main supporting arm of a conventional glass polishing machine 19 isindicated in FIGURE 4, the arm 20 having a plurality of rotating,polishing spindles such as 21, each carrying a circular polishing blocksuch as 22. In the plate glass industry, the glass sheet 23 is adheredby plaster 24 to a carriage 25, the upper face 26 of the glass beingpolished by the polishing faces 27 of the felt polishing pads 2S. Thepolishing blocks 22 are usually lof metal, with a flat, circular lowerface 29 covered by the polishing felt and a smooth, cylindrical outerside wall, or peripheral n'm, 30. The conventional, relatively thin,square polishing felt, is not more than one inch thick so that its fourcorners can be bent upwardly to be locked in place by a locking ring 31,hydraulically pressed over the felt corners and block. Felts of greaterthan one inch thicknness have heretofore not been mechanicallyattachable by a locking ring 31, due to the stiffness and lack ofbendability of a thick felt pad, and have therefore been thick, solidcylinders adhesively attached flatwiseito the lower face 29 of theblock.

The preformed, crenelated, composite polishing pad 28 of the invention,is of predetermined diameter and height, or thickness, to t on the block22 and to be mechanically attached thereto by the locking ring 31.

Pad 28 includes the outer retaining, or attachment, ring 34, ofpolishing felt, the ring 34 being generally cylindrical and having ahollow cylindrical lower wall portion 35 and an integral, interrupedupper wall portion 36, outlining a hollow 'cylinder and forming a recess37 to receive the polishing block 22.

vThe hollow, cylindrical, lower, wall portion 3S, encircles the mainbody 38 of pad 28, the body 38 being disc, or solid cylindrical, inconfiguration and preferably formed of a plurality of strips ofpolishing felt, 39, 40 or 41 each upstanding on its lower edge 42, 43 or44, the latter forming part of the circular polishing face 27 of the padand being coplanar with the lower, annular, polishing edge 45 of theouter 'ring 34, The upper edges 47, 48 or 49 of each strip 39, 40 or 41,and the top of the lower wall portion 35 of ring 34, all terminatesubstantially in a common plane, central of ring 34, and parallel to theplane of lower face 27, the central plane being indicated by dotted line50. The strips V39, 40 and 41 are preferably closed, annular rings offelt having a wall thickness corresponding to the wall thickness of ring3'4 of about one inch but being substantially greater than one inch inheight, for example from two to four inches. The outside diameter of thebody 28 is substantially equal to the diameter of the block wall 30 sothat the upper face of body 28 is substantially coextensive in area withthe face 29 and the inside diameter of the upper wall 36 issubstantially equal to that of wall 30 to closely t therearound.

The endless, closed, individual felt rings 39, 40 and 41 Vin the outerperipheral portion of body 38, tend to prevent rupture of the ,pad fromlateral polishing forces. Each is of progressively smaller diameter fromthe outside to the inner ring 41. The inner ring 41 is preferably filledwith juxtaposed, parallel, straight, edgewise-upstanding felt strips 51,52 or 53 to increase the spread of the slurry in a radial direction fromthe rotational axis to the outside of the pad. The lower polishing edges54, 55 and 56 are in the plane of the lower face 27, all of the strips39, 40, 41, 51, 52 and 53 are of uniform height and all of their upperedges 57, 58 and 59 are in the central plane 50 to form a flat,circular, felt, upper face `60 on body 3S and in central plane 50.

The continuous, annular, lower wall 35 of ring 34 circumferentiallyencircles the disc shaped main body 38, and the upper wall 36 of ring 34extends upwardly from the central plane 50 to the plane of the top ofthe outer wall 3i) of block 22. Upper wall 36 could be a continuous,upstanding, self-supporting, rim-like flange of polishing felt butpreferably it is interrupted, or crenelated, to form at least fourcircumferentially spaced iutegral attachment tabs, 63, 64, 65 and 66,one in each quadrant and each of less angular length than the length ofone of the spaces `67, 68, 69 or 70 therebetween.

I use the term crenelated to mean a Wall consisting of a series ofalternate solid parts and open spaces, upstanding from, and extendingaround the upper, peripheral edge of a body, the solid wall parts beingformed of the material of the body. It will be seen that the tabs 63,64, `65 and 66 are preformed to be inherently upstanding around the edgeof the pad 28, without requiring upbending or distortion of the feltmaterial and that the tabs are self-supporting, relatively thick andresiliently yieldable to slightly compress under the pressure exerted bythe locking ring, as indicated at 72 in FIGURE 4. A corresponding bulge73 or 74 occurs in the felt of the tabs, above and below the ring 31,and each felt tab such as 66 also bulges as at 75 into the spaces 69 and70 on each side thereof, this resilient wedging action serving to clampthe ring 31 more firmly in place,

Each tab, such as 66, is preformedv to be arcuate in plan therebyconforminng to the hollow, cylindrical shape of the wall 30 of block 22and preferably the side edges 76 and 77 of each tab, such as 66, areslightly beveled, or tapered. The inner felt faces of the tabs aredesignated 78, 79, 80 and 81.

Reinforcing backing means 8S is provided as a covering over the upperface `60 of the body 38 and over the inner faces 78, 79, v8() and 81 ofthe upstanding felt tabs to unitize the pad 28, While protecting theblock 22 from the slurry. Means 85 is preferably a doubled layer ofheavy canvas duck 86 and 87 adhesively united to a doubled layer ofcured rubber 88 and 89, the cured rubber bonding the duck layerstogether and bonding the doubled backing to the felt body fand tabs. Asshown in FIGURE 5, the plurality of reinforcing layers 86, 87, 88 and 89are preferably in the form of four superposed flat discs of sheetmaterial alternately of partially cured rubber and canvas duck, the tabportions being separate patches such as 90, each extending upwardly asat 91 and each having a base portion 92 interleaved between the disclayers.

As shown in FIGURE 6 the crenelated, felt pad 28 is fabricated `by firstforming 'the closed, annular ring 34, of felt, in a diameter to litaround the side wall of the block 22 and then cutting, or otherwiseforming, at least two and preferably four, tabs 63, 64, 65 and 66 in theupper portion. The lower, continuous wall portion 35, of ring 34, isthen filled with juxtaposed strips of felt upstanding on the lower edgeand preferably forming concentric rings in the outer periphery andstraight strips in the central portion. The reinforcing backing means isthen placed within the recess 37, of the crenelated felt pad, to form acrenelated backing therefor, overlying the upper edges of the feltstrips and the inner faces of the felt tabs. The assembly is then placed-between the hydraulic press platens 94 and 95, which are steam heated,and subjected to pressure of about 50 p.s.i. at a temperature of about230 F. for about thirty minutes. The partially cured rubber layers, thusare completely cured while permanently bonding all of the layers ofcanvas, rubber and felt into a unitary, composite, preformed crenelatedpolishing pad of substantial thickness.

At least one, and preferably two, compression bands 96 and 97, extendcircumferentially around the outside face `98 of the lower wall portion3S, the bands being about three quarters of an inch in width and thelower band being spaced about three quarters of an inch above the planeof the lower polishing face 27. Bands 96 and 97, in cooperation with theconcentric rings of felt of the pad tend to support the pad againstundue lateral displacement during the polishing operation. The band 96in the upper section, and the band 97 in the lower section, of lowerwall 35, exert sufficient inward force to permanently compress the lowerwall 35 into truncated conical coniiguration. Preferably the compressionbands are wrapped around the ring 34 prior to placement of the assemblyinto the press for curing, and they -may be of any soft, strong materialsuch as reinforced rubber or the like. Bands 96 and 97 mayadvantageously be made of five cords of viscose rayon cemented togetherby a suitable adhesive, the heat and pressure of molding tending to meltsome of the cement holding the cords together, thereby causing someadhesion to,

the felt surface of ring 34.

As best shown in FIGURE 1, an elongated filler strip 99, of uncuredrubber, may be inserted along the corner between the inner face of eachfelt tab and the upper face of the body 38 to round off the bend in thebacking means 85, at this location and thereby add resistance to padfracture.

In any case, the rounded edge of the mold head 94 and the resiliency ofthe felt fabric and rubber tend to form a fillet, in the area occupiedby strip 99, if no such strip is used, thus producing a concave junctionbetween the meeting surfaces.

I claim:

1. A preformed composite polishing pad for attachment to a glass machinepolishing block having a peripheral exterior rim of predetermined heightand diameter, said pad comprising:

a hollow attachment ring of polishing felt, said ring having a lowerwall portion upstanding from the plane of a lower, annular polishingedge to a central plane, parallel thereto and at a height thereabove ofsubstantially greater than one inch and an integral, unitary, upper,wall portion, defining a hollow cylinder of predetermined height anddiameter terminating in a plane substantially above the planes of saidlower wall portion and having an inner face adapted to be coplanar with,receive and encircle the rim of said block;

a disc-shaped body of polishing felt filling the space within the lowerwall portion of said attachment ring, said body having a lower, circularpolishing face coplanar with the lower polishing edge of said ring andand an upper face in the central plane of said ring;

a unita-ry, cured rubber and fabric backing covering,

and adhesively united to, the upper face of said discshaped body and tothe inner face of t-he upper wall portion of said ring, and

at least one compression band, extending entirely around the outsideface of the lower wall po-rtion of said ring, at a spaced distance abovethe plane of the lower polishing face, of said body for supporting thefelt thereof against lateral displacement.

2. A composite polishing pad as specified in claim 1 wherein:

said disc shaped body of polishing felt is formed of a plurality ofjuxtaposed felt strips, each upstanding on a lower edge coplanar withthe lower polishing face thereof, and each of uniform height above saidface.

3. A composite polishing pad as specified in claim 1 wherein:

said disc shaped body of polishing felt is formed off a plurality ofindividual, endless, rings of felt in the outer peripheral portionthereof, each concentric with said felt attachment ring and ofprogressively smaller :diameter from said attachment ring to an innerring and said inner ring is filled with a plurality of straight,parallel st-rips of felt each upstanding on lo the lower edge thereof;

whereby said rings offer resistance to lateral displacement of said padduring polishing and said straight strips offer assistance to the spreadof slurry during polishing.

4. A composite polishing pad as specied in claim 1 wherein:

the upper wall portion of said retaining ring comprises four,circu-mferentially spaced, upstanding tabs, one in each quadranttherearound and each of arcuate section in plan, said tabs defining aho-llow cylinder and being compressible into .the spaces between thetabs under the pressure of the locking ring of said polishing block.

5. A composite polishing pad as specified in claim 1 wherein:

said unitary cured, rubber and fabric backing comprises a plurality ofalterna-te layers of cured rubber sheeting and heavy, closely woven,canvas adhesively united toeach other and to a filler strip of rubberextending around the periphery of the upper face of said body proximatethe central portion of the inner face of said felt retaining ring toconform said pad to the curved edge of the rim of said block.

6. A composite polishing pad as specified in claim 1 wherein:

said body is several inches in thickness and there are two saidcompression bands, one in the upper section and one in the lower sectionof the lower portion of -the wall of said retaining ring, said lowerband compressing said pad into truncated conical configuration.

7. A preformed, composite, polishing pad for a glass polishing blocksaid pad comprising:

a relatively thick disc-shaped body of polishing felt, said body havinga flat, lower polishing face and an opposite upper face, in a plane `ata spaced distance above said lower face, said faces being substantiallycoextensive in area with said block;

an outer attachment ring of felt, said ring having a hollow cylindricallower wall coplanar with, and circumferentially encircling saiddisc-shaped body and having at least two oppositely disposed, felt,attachment tabs integral with said wall and inherently upstandingtherefrom to a plane at la spaced distance Aabove the plane of saidupper face of said body, said tabs being preformed with an arcuatesection in plan;

at least one unitary reinforcing layer of cured rubber and fabriccovering the inside face of said tabs and covering the upper face ofsaid body,

and at least one compression band extending circumferentially aroundt-he outside of the lower wall of said ring, at a spaced distance abovethe lower face of said pad, for resisting lateral forces on said pad.

8. A composite polishing pad for a glass polishing block,

said pad comprising:

a cylindrical body of polishing felt substantially coextensive in areawith the face of said block and of 'a thickness substantially greaterthan one inch;

-a continuous hollow cylindrical ring of relatively thick polishing feltextending peripherally around said body and vencircling said body, saidring having a plurality of preformed self-supporting, spaced-apart, tabsof said felt, integral with said ring and extending upwardly therefromto define a block receiving recess with said body;

a reinforcing, fabric layer lining the inner face of said recess andadhesively united to said tabs and body,

and compression band means unitizing the felt of said ring and body forresisting lateral forces on said pad.

9. -n combination:

a circular glass polishing block;

a composite polishing pad, of felt substantially greater than one inchin thickness, covering the polishing face of said block;

a felt ring encircling said pad, said ring having a preformed,upstanding interrupted, self supporting, integral rim-like flange ofsaid felt, said interrupted felt flange extending around the peripheralWall of said block to form spaced attachment tabs of felt;

reinforcing means for 'unitizing the felt of said ring,

ytabs and pad, and

a locking ring encircling said felt attachment tabs on said block forfirmly securing said pad thereon.

References Cited UNITED STATES PATENTS DANIEL BLU-M, Primary Examiner.

9. IN COMBINATION: A CIRCULAR GLASS POLISHING BLOCK; A COMPOSITEPOLISHING PAD, OF FELT SUBSTANTIALLY GREATER THAN ONE INCH IN THICKNESS,COVERING THE POLISHING FACE OF SAID BLOCK; A FELT RING ENCIRCLING SAIDPAD, SAID RING HAVING A PREFORMED, UPSTANDING INTERRUPTED, SELFSUPPORTING, INTEGRAL RIM-LIKE FLANGE OF SAID FLET, SAID INTERRUPTED FELTFLANGE EXTENDING AROUND THE PERIPHERAL WALL OF SAID BLOCK TO FORM SPACEDATTACHMENT TABS OF FELT; REINFORCING MEANS FOR UNITIZING THE FELT OFSAID RING, TABS AND PAD, AND A LOCKING RING ENCIRCLING SAID FELTATTACHMENT TABS ON SAID BLOCK FOR FIRMLY SECURING SAID PAD THEREON.